Air conditioning system



I w. 1-1.. CARRIER Nov. 28, 1944.

AIR CONDITIONING SYSTEM 5 Sheets-Sheet 1 Original Filed Aug. 12, 1939 BY 4mm FIG.

W. H.- CARRIER AIR CONDITIONING SYSTEM Nov. 28, 1944. 2,363,945

Original Filed Aug. 12, 1939 5 Sheets-Sheet 2 INVENTOR. lw zao @Mw,"

Nov. 28, 1944. w. H.- CARRiER 2,363,945

AIR CONDITIONING SYSTEM Original Filed Aug. 12, 1939 5 Sheets-Sheet 5 FIG. 4

INVENTOR. 42d; v BY 444,. RM

'Nov. 28, 1944. w. H. CARRIER AIR CONDITIONING SYSTEM Original Filed Aug. 12, 1939 5 SheetsSheet 4 IRA 2. k iw ,7 MN RII. 9

' INVENTOR. 4% a,

5 Sheets-Sheet 5 o-|os ZIO W. H.- CARRIER AIR CONDITIONING SYSTEM Original Filed Aug. 12, 1939 Nov. 28, 1944.

' Patented Nov. 28, 1944 AIR CONDITIONING SYSTEM Willis H. Carrier, Syracuse, N. Y., assignor to Carrier Corporation; Syracuse, N. Y., a corporation of Delaware Original application August 12, 1939, Serial No.

289,749. Divided and this application July 7,

1942, Serial No. 450,054

8 Claims.

This invention relates to air conditioning and is a division of application Serial. No. 289,749.

filed August 12, 1939.

The general object of the invention is to provide improvements in conditioning of air for rooms of ofiice buildings, schools, hospitals, apartments, hotels and the like.

It is an object of the invention to provide required cooling under summer operating conditions and required heating under winter operating conditions, while at all times maintaining a desired dewpoint or atmospheric moisture Content within a plurality of conditioned enclosures.

It is another object of the invention to provide improved accessories for producing desired conditioning during winter and summer seasons, and also, during intermediate seasons, whereby difierent enclosures may simultaneously be heated and cooled whenever such differential action is required by load conditions affecting the several enclosures served by the system. I

It is another object of the invention to provide an improved air conditioning system which assures positive and adequate ventilation at all times of the area or enclosures served thereby.

It is another object of the invention to pro vide an air conditioning system employing a plurality of local units severally disposed in or proximate the areas which are to be served by said units, said units containing no motors, compressors, fans or other apparatus of a similar nature, and being entirely free of moving parts, thus giving assurance of long life, silent operation and freedom from operating difliculties and mechanical break-downs.

It is another object of the invention to pro vide an air conditioning system which is particularly well adapted for installation in existing structures at relatively low cost, and which also is well adapted for installation in new structures.

It is another object of the invention to provide an air conditioning system 'for conditioning a plurality of areas or enclosures in which a portion of the air delivered to-said areas. or enclosures-is conditioned at acentral point, but in which the distribution of such air is efi'ected without resort to conventional ducts of large sizes, the air conditioned at the central point in accordance with the present invention being supplied through conduits of relatively small dimensions and occupying relatively little space. In ofilce buildings and the like, where space is at a premium and rentals are based on the floor of space effected by the present invention is of great importance.

It is another object of the invention to provide an improved air conditioning system for conditioning a plurality of enclosures in which a portion of the required conditioning is: effected at a central conditioning point remote from the enclosures and the remainder of the required conditioning is-effected by apparatus of the unit type disposed in and serving the various enclosures conditioned by the system.

Broadly stated, the invention includes conditioning to a desired degree a first volume of air at a central conditioning point, and distributing this air at relatively high static pressure and at relatively high velocity to a plurality of units respectively disposed in and serving a plurality of areas or enclosures to be conditioned. The high pressure air supplied to each unit is discharged therein through nozzle formations or the like, and in this manner induces a relatively great secondary circulation of air withdrawn from the area served by the unit. The primary or high pressure air and the secondary or intion;

area available for useful purposes, the saving duced air are then supplied to the conditioned area. Preferably, the primary air is conditioned to a predetermined dewpoint at the central conditioning point, and tempering means, such as coils or the like, are disposed in the various local units to efiect sensible cooling or heating of air circulated through theunit as required. The primary air preferably comprises outdoor air, and since in carrying out the invention it is preferred to use approximately one part of primary air for each four parts of secondary air supplied to each conditioned enclosure, adequate ventilation of the enclosures served by the system 'is thus assured- These and other features, objects and advantages of the invention will more fully appear from the following description to be read in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic view illustrating an air conditioning system embodying the inven- Fig. 2 is a front elevational view, partly in section, of one of the local units adapted to be employed in carrying out the invention;

Fig. 3 is a view of the unit of Fig. 2 taken on the line 33 thereof;

Fig. 4 is a view in plan of the unit of Figs. 2 and 3, part of the casing being broken away to show the interior of the unit;

Fig. 5 is a view illustrating, in section, a valve adapted to modulate the cooling or heating action of the local units in response to changes in load requirements, and diagrammatically illustrates the piping connections to and between this control valve and the heat exchange coil of the conditioned unit;

Fig. 6 is a fragmentary view in end elevation of the interior of a unit in accordance with the invention, illustrating an indicator mechanism adapted to be employed when control of the local unit is effected manually rather than automatically;

Fig. Us a view in plan of the control mechanism shown in Fig. 6;

Fig. 8 is a view in perspective of a portion of the control mechanism of Figs. 6 and 7;

Fig. 9 is a fragmentary view, in perspective, of a riser employed in carrying out the invention, and a lateral connection thereto, the latter being shown in an exploded view;

Fig. 10 is a view in vertical section through an assembled lateral air connection, taken on th line lll-l0ofFig.9;

Fig. 11 is a view on an enlarged scale, taken on the line llll of Fig. 9, illustrating the joint formation in the vertical riser;

Fig. 12 is a view in horizontal section through one of the channels housing the air riser and water supply, return and drain pipes, which extend upwardly from the central station apparatus for connection with the various local units of the apparatus;

Fig. 13 is a view in vertical section of-a baseboard construction adapted to contain and conceal the laterally extending air conduit, water supply, water return and drain pipes, taken on the line l3-l3 of Fig. 14;

Fig. 14 is a view in perspective of the corner of an enclosure served by apparatus in accordance with the invention, illustrating the baseboard assembly; I

Fig. 15 is a view in perspective, of a baseboard spacer element:

Fig. 16 is a view in vertical section through a manual control valve adapted to be employed in carrying-out the invention, and incorporating a modified indicator mechanism in conjunction therewith; and

Fig. 17 is a view in plan of-the control knob of the apparatus of Fig. 16.

Referring now to the drawings, similar numerals referring to the same or similar parts, the numeral designates generally a casing containing air conditioning apparatus of any desired type, and disposed at any desired pointin or proximate abuilding to be conditioned. Thus, for example, the casing 25 may be disposed in the cellar, attic or storage space of a building served thereby. A fan 28 draws air through the casing, preferably from the outdoor atmosphere, whereby the air is conditioned in desired manner during its passage through the casing 25, and then discharges this air at relatively high static pressure into the primary high pressure air main 2 The conditioning apparatus in casing 25 may ing coil 23 and a reheating coil 30. -Cold brine or other suitable conditioning medium is supplied tothe coil 29 through supply line 3| and is withdrawn therefrom through return line 32. underthe influence of pump 33 which returns the liquid 5 cooled refrigerant. Reheating coil receives a i be of any desired type and it is to be understood heating medium, such as steam, from supply main 36 through branch line 31 under the control of valve 38 controlled by thermostat 39. Ihe valve 38 admits steamto the coil 30 in a quantity sufficient to maintain the temperature of the air leaving the casing 25 at a desired point, thus reducing the relative humidity of the air leaving the cooling coil 29. Preferably the conditioner casing 25 contains also a preheating coil 49 adapted to receive steam from main 36 under the control of valve 4| controlled by a thermostat 42 disposed within the conditioner casing, the preheating coil 40 being intended for use under winter operating conditions. The conditioner casing preferably also contains humidifying sprays or the like 43 operative under winter operating conditions to increase the moisture content of air passing through the conditioner casing.

The pipes 44 and 45, respectively connected to 5 pipes 32 and 3|, and respectively served by valves 48 and 41, may be 'used for connectin into the circuit of the cooling coil 29 a connection to a source of well water, ice-water storage tank, or a cooling tower or the like for use when the wet bulb temperature of the outdoor air is sufficiently low to permit the use of evaporative cooling instead of the refrigeration normally supplied in any desired manner to the cooler 35. It will be understood that when the valves 46 and 41 are opened, the-valves 48 and49, respectively located in lines 32 and 3 I, will be closed.

Preferably a closed expansion tank 50 is connected by line 5| to the refrigerant return line 32, the closed expansion tank containing a quantity of compressible medium such as air and being employed at a low point in the liquid circulating system. It will be understood that if desired an open expansion tank may be used at a high level in the system in the same manner as employed, for example, in connection with hot water heating systems.

As noted above, control of the operation of the local units may be effected either manually or automatically. For purposes of illustration, the section of the system indicated within the dotted lines and designated zone A in Fig. 1 of the drawings, will be described with particular reference to automatic control, while the section of the system indicated within the dotted lines and desig- 5 nated zone B, will be described with particular reference to manual control. It is to be understood that each zone of the conditioning system may comprise any number of local condition units, and that any number of zones may be proerable that the zones of thesystem be arranged in accordance with the heat loads affecting the different enclosures of the conditioned building. 5 For example, in an omce building all of the offices having windows facing in an easterly direction would be subject to the heating effect ofthe sun early in the day, whereasthis heat load due to sun effect will fall off later in the day. All or a number of such oilices might well be served, in accordance with the invention, by local units comprising a single zona lmthesame way the oihces having windows facing in a southerly direction ar'preferably served by units compris- 5 ing another zone of the conditioning system,

etc. Of course, other factors than sun effect may have dominating importance in this connection. Thus, if certain rooms are ordinarily occupied to a great degree, whereas other rooms are ordinarily occupied to a lesser degree, it might be desirable to arrange the zoning of the various units with reference to these factors so that desired simplicity and uniformity of control may readily be achieved. In such case units having a high heat load would form one zone and units having a low heat load would form another zone.

It is to be understood that the units comprising a zone of the system may be located on different floors, or on the same floor, or both, and that any number of units may be incorporated within a zone. The nature of the zone controls and the interconnection of the various units with the central station conditioning plant, will now be described in detail. r

The air delivered by the fan 26 to the primary air distributing main 21 is at a relatively high static pressure, of the order of of water.

A portion of this air is diverted from the primarymain 21 and passes to a vertical riser 52 of zone A and a corresponding riser 52 of zone B. Each 53 through lateral connections such as 66, and this water may then be returned through pipe 61 to the cold water retumline 32 at the suction side of, the pump 33. When the control device 51 reflects a demand for maximum cooling, the valve 59 will be adjusted so that the pump 60. draws water only from header 56, and in this case also all of the water returning from the local units through the pipe 61 will pass to the water return line 32. However, if the cooling load is less than maximum, the proportiom ing valve 59 will be adjusted to an intermediate position determined by the cooling load, in which vertical riser delivers air to a plurality of units designated generally as 53, through lateral connections 54. The primary air thus delivered to each unit serves to induce a relatively great circulation of secondary air and to promote desired circulation of air in the conditioned enclosures.

A pipe 55 connects with the cold water return line,32 and is adapted to deliver cold water or' brine from said return line to cold water supply- .conveniently located at any desired point either within or without the enclosures of the zone served thereby. In practice it has been found expedient to position the control device 51 outside of the building, or in such manner that it is subject to outdoor atmospheric conditions. Preferably, the control instrument 51, comprises a device known as the Aerotherm, manufactured by Webster-Tallmadge 8: Co., Inc. Since this control device is well known in the art and does not, per se, form part of the invention, no detailed description thereof is deemed required here. It is to be understood, however, that the control device 51 preferably responds not only to air temperatures, but also to air velocity, wind direction, etc., so that the device controlling each zone may accurately reflect the need either for cooling or heating of the particular zone served thereby, and may at'least approximately indicate the degree of heating or cooling which is required.

When the control device 51 serving zone A indicates a demand for cooling of the enclosures served by the local units 53 of zone A, control line 58 leading from the control device 51' serves to open the three-way or proportioning valve 59 Q ratus if this should be desired.

the pump 60 will draw water not only through pipe 6| from the header 56, but also through bypass line 69 leading from the water return line 61. It will be understood that the control device 51, by varying the proportions of water drawn from the supply header 56, and from the return line 61, will efiect a variation in the temperature of the water delivered to the unitsin accordance with variations in load requirements.

Under winter operating conditions, or whenever heating is required, as indicated by the control device 51, the proportioning valve 59 is so adjusted that the pump 66 draws water only through the bypass connection 68 from line 61. The water then delivered from the pump passes to the proportioning'valve 65 through line 62 or line 69, or both, in varying proportions controlled by the valve 65 under'control of device 51. The line 63 contains a heater =1ll which receives steam from header 36 under .the control of valve 1|, the valve 1| preferably being controlled by the control device 51 as indicated by the dotted line 12 leading to the control line 64.

The valve 1| is normally fully open whenever heating is required, the modulation of heating effect being accomplished by the routing of different portions of water through the heater 1!! and through the pipe 62.

Under summer operating conditions the water 1 discharged fromthe valve 65 passes to the units through line 63'and is returned therefrom through "line 61. However, under winter operating conditions when automatic control of the local units 53 is employed, as in zone A, it is preferred to reverse the circulation. Thus, under winter oper- -ating conditions, hot water delivered from the proportioning valve 65 is routed through crossover pipe 12 to pipe 61 by suitable adjustment of so that the pump 66 draws cold water from the header 56 upwardly through'pipe 6! and delivers three-way valve 13, and water returning from the local units passes through pipe 63, thence through cross-over pipe 14' by suitable adjustment of three-way valve 15, and then returns to the inlet of pump through line 68.

Suitable shut-off valves 16 and 11 are provided for isolating the entire piping arrangement of each zone from the central conditioning appa- Under.winter operating conditions when no cooling is required, the circulation through the cooling coil 29 of the central station conditioner 25 isdnterrupted and in such case the shut-oil valves 16 and 19 are closed to isolate the central station water circulating system from the waternected with the water circulating systems of the 8 various zones, valve 89 is closed.

The piping and control arrangement for zone B, in which the units are controlled manually, is substantially as described in connection with zone A, except that it will be noted that valves I3 and I5, and the cross-over pipes 12 and 14, are omitted. In all other respects, the piping arrangement and basic control scheme is the same as described in connection with zone A, and therefore no detailed description is deemed required with respect to zone B.

Referring more particularly to Figs. 2, 3 and 4, illustrating one of the local units adapted to be employed, the numeral 82 designates generally a cabinet having an air inlet grille 83 formed in the front upper portion thereof and extending across a major portion of. the length of the casing. Also an air outlet grill 84, comprising a plurality of vanes or louvres extending lengthwise of the easing, is provided in the top of the casing 82. Formed within the central portion of the casing 82 is an air plenumchamber 85 to which air is i delivered through inlet 86 from lateral connection 54 extending from one of the vertical high pressure air risers. 'A valve closure member 81, operating in conjunction with valve seat 88, serves to control the volume of air admitted within the plenum chamber 85 and to-effect the desired degree of pressure reduction. The valve closure member 81 is adjusted by means of a in desired position by *a pair of lock nuts. 99 which are tightened after the bottom projecting portion 9| of the valve stem has been turned to provide the desired degree of valve opening. In

I operation, once the valve has been adjusted to provide the desired static pressure within the plenum chamber, it remains fixed in position.

However, if it is desired for any reason to cut the unit out of service, the valve is closed so that no air will be discharged through such unit, while the system is used for delivering high pressure air to other of the units continuing in active service.

Preferably, the interior of the plenum chamber 85 is provided with a' plurality of sound absorbing baiiies 92 constructed of anysuitable sound absorbing material, which cause the air delivered provided, at its upper extremity, with a plurality of spacedrelatively small nozzles or orifices 94 'f in diameter or smaller, through which air is valve stem 89 preferably threaded and secured discharged upwardly at relatively high velocity.

' In accordance with principles which are. well understood, the high velocity discharge of air through the nozzles 94 induces a relatively great circulation of .air intaken within the unit through the inlet grille 83, the air discharged at high I velocity and the induced an mixing in a mixing chamber 95 and then being discharged from the unit through the outlet grille 84. The induction of air within the unit and its discharge there-' from insurev active circulation in the enclosure served thereby. l

To prevent drafts or spilling of cool air in the vicinity of the unit, there are provided a plurality of diffusion vanes 99 proximate the discharge outlet 84, and these are preferably arranged in a fan-shaped manner at varying angles, as best seen in Fig. 2. The diffusion of air lengthwise of the unit by the vanes 96 serves eifectively to insure equable conditions within the enclosure without danger of drafts caused either by spilling or by impingement of the air stream against a relatively low ceiling or beam and resultant downward deflection. When the unit is employed in the center of a wall area the vanes are symmetrically arranged as shown in Fig. 2, but if the' unit is employed at the end of a wall area it may i be preferred to have the vanes which are closest the end wall vertical and the other vanes correspondingly inclined,'the vanes farthest from the end wall most closely approaching the horizontal. While the vanes 96 may be formed in any desired manner, they are preferably punched from a solid plate 91, the resultant apertures 98 serving as air passages.

Within the casing 82 at the inside of the inlet grille 83 is disposed a suitable heat exchange means of any desired type for conditioning the air induced within the unit by the discharge of primary air from the nozzles 94. Preferably, the heat exchanger comprises coil 99 provided with suitable plate or spiral fins for increasing the.

efiiciency of heat transfer. It is to be understood that if desired, the-coil may be placed in the path of the primaryair, as well as in the path of the induced air.

In Figs. 2,, 3 and 4 the piping and control arrangement shown is that employed when the unit.

59 is controlled manually. Water supply line 86 extends within the unit from vertical riser 63 l and passes ,to a shut-off valve I99. Water return connection I M returns to pipe 61 from valve I99. The valve I99 is a twin valve which serves to interrupt flow through both the supply line 66 and return line IN by means of a single adjustment of the valve stem I92. I

The numeral I93 designates generally a control valve, the construction and operating mechanism of which are described more fully hereinafter. For present purposes, however, it is sufli-.

cient to understand that the valve is provided with three connections-an upper connection I94, a center connection I95 and a bottom connection I96. A water supply line I91, constituting a continuation of the supply line 66, delivers water to central connection I95 of the valve I93. Some of this water thus delivered to the valve is discharged from the valve through pipe I96 and thus is delivered to the heat exchange coil 99. The water leaving the coil is returned to return pipe I99 through a'connection indicated at II9. Water which is not supplied to the heat exchange coil 99 after supply to the valve I93, is bypassed from the valve back to the return pipe I99 through bypass return pipe I I I, leading from valve opening I96. By regulation of the valve I93 by means of handle H2, varying proportions of the water delivered to the valve may be routed through coil 99 and through the bypass connection III. In any event, however, regardless of the adjustment of valve I93, water is supplied to each unit through the supply pipe 86 and returned therefrom through the return connection I9'I at a constant rate. Thus, the friction losses are maintained constant and the system therefore may be hydrostatically balanced to give results superior to those obtainable where the rate of flow to and from a unit is varied inaccordance with load requirements. This latter operation may be employed if desired but it is to I therein.

2,363,946 be understood that the operation described above,

in which the system remains balanced at all times, is preferable.

Preferably, the coil 98 is provided with an air vent or the like 3 at the upper portion thereof to relieve air from the system. I

In the operation of the central station conditioning apparatus, the primary air is reduced to a low dewpoint. When water or brine is used for this purpose in the manner illustrated in Fig. 1,

the heat exchange surface is so designed that the brine returning from-the coil 29 is at a higher temperature than the air leaving the conditioner casing 25. Since it is the brine from return line 32 which is supplied to the local units 53 to effect cooling thereat, it will be appreciated that the brine delivered to the local units will generally always be above the dewpoint of the air in the conditioned enclosures so that no moisture will be condensed in the local units. This is true in all cases except on starting up of the system in a humid atmosphere or where there is a relatively high latent heat load in the conditioned enclosure tending abnormally to increase the moisture content of the air therein.

To accommodate the water which from time to time may be precipitated by the coil 99 there is provided a drain pan II4 adapted to catch any water dripping therefrom. The front portion of the drain pan II4 discharges the collected moisture into a trough II5 which slopes downwardly toward the right hand side of the casing, as best seen in Fig. 2. From the low point of the trough II5 a drain connection II6 conveys condensate downwardly to an auxiliary condensate pan III lows I25, the lower extremity of the bellows being secured in a fluid-tight manner to a disc I26.

' The pressure tube I20 leads from the interior of the thermal element H9 to the interior of the bellows I so that as the temperature affecting the control element I I9 is varied, the bellows I25 is caused correspondingly to expand and contract. A stud I21 extends within the interior of the bellows to decrease the free volume in the bellows, as this insures a more prompt and sensitive operation of the valve. The disc I26 is connected to a rod I28 extending downwardly therefrom and bearing a flange I29 atits lower extremity. The rod I29 extends within a cupwhich is disposed beneath all of the apparatus in the casing 82 to catch any condensate which may drip therefrom. The bottom of the pan II'I slopes downwardly toward the front of the unit and a drain connection I I8 conveyswater therefrom for disposition in any suitable manner.

Preferably, the drain pipes extend from the various local units to a suitable point of condensate disposal in the manner indicated, for example, in Fig. 12. Thus, it is to be understood that the piping arrangement of Fig. 1 actually might also include the common drain pipes used for the various units. However, this feature has not been shown in Fig. 1 as it would tend unnecessarily to complicate the showing of the invention made Referring more particularly to Fig. 5, the numeral I03a designates a valve capable of automatically modulating the heating or cooling effect of the coil 99 of the local unit 53. The control element which is preferably used in conjunction with the valve comprises a length of finned tubing II9 of the type commonly used in the construction of heat exchangers. The length of the control element may approximate 8" and the diameter of the tube may be of the ,order of /2. One end of the tube is sealed and the other end connects with a pressure tube I20 which extends within the housing I2I of the valve I03a. The control element II 9 is filled with a volatile fluid adapted to expand and contract with changes in temperature, such as ether, and the control element H9 is placed within the cas.. ing 82 behind the air inlet grille 03 and in the path of air intaken within the unit through said grille, so that the control element reflects the temperature within the enclosure served by the unit. The control element is preferably shielded in any desired manner from the heating or coolshaped member I30 and the flange I29 provides for retention of the rod I28 within the member I30 so that as the rod I28 is raised the member I30 will be raised correspondingly. ;A spring I3I, extending between the bottom of disc I26 and the top of member I30, tends to maintain maximum separation of these two elements. The

lower portion of member I30 carries a disc I3Ia to which there is connected, in a fluid-tight manner, a sealing bellows I32, and also arod I33 extending through a plate I34 to which the bellows I32 is connected. Thus, the operating fluid of the thermal element is prevented from escaping within the valve and also the water or brine controlled by the valve is effectively prevented from escaping within the valve.

The rod I33 bears downwardly upon a lever I35 pivoted at I30. The free end of the lever I35 bears downwardly upon a lever I31, pivoted at I38, at a point proximate the fulcrum I38. The lever I3! is adapted to actuate thevalve stem I39 which is operably connected through a starshaped guide I40 to a'valve closure member I M,

comprising a pair of oppositely arranged faces I42. Thev arrangement of levers I35 and I3! is employed for the purpose of multiplying the motion of the primary control rod. Thus for a given movement of the valve rod I33 the corresponding movement of valve rod I39 may be four or five times as great. This amplification makes fo increased sensitivity and refinement of control and makes it possible to maintain within very close limits the desired temperature in the conditioned enclosure.

The valve seat serving the upper face I42 is formed in a partition plate I43 provided between the upper connection I04 and the center connection -I05 of the valve. The seat I 44, cooperating with the lower face I42 of the valve member MI, is disposed between the central connection- I05 and the bottom connection I06 of the valve. Spring I45, operating on valve guide I45, biases the valve in an upward direction.

, Under summer operating conditions, or whenever cooling is required, a temperature higher than that desired required an increased flow of cooling medium through the valve. Under winter operating conditions, however, a temperature higher than normal calls for a decreased rate of flow of heating medium through the coil. To render the local unit entirely automatic so that its single valve may provide for the accurate conin the case of automatic operation.

manner just described, since an operator can with cooling medium, if the temperature in the enclosure served by theunit is too high the op- Under summer operating conditions, as explained in connection with Fig. 1, cooling me-- dium is supplied through line 63, and thus enters the valve through the central connection I05.

. Assuming a demand for cooling to exist, the high temperature affecting [the control element I I9 will cause depression of the valve MI and thus some of the liquid entering the valve at connection I05 will flow upwardly and out of the valve through I04 and through line I41 to the heat exchange'coil 99. The conditioning medium passing from the coil is routed through line I48 to junction 9 and thenpasses through pipe I50, containing check valve I50a, to line 61 and is thus returned from the local unit. The portion of the conditioning medium supplied to the valve which is not so routed, passes downwardly in the valve past the valve seat I44 and is discharged through connection I 06 to line I5I through which it passes to junction I49, where this fluid is joined with the fluid discharged from the conditioning coil 99 and is returned therewith .to the line I51.- As more conditioning-is required under summer operating conditions, more cold liquid is circu-- lated through the conditioning coil 99 and less is bypassed through I05, and as less conditioning is required less cold liquid will be supplied tosthe coil 99 and more will be bypassed through Under winter operating conditions reverse operation occurs, and in this case an increased temperature aifecting the thermal control ele-' ment II9 results in decreased supply of conditioning medium, which is then at a relatively high temperature, to the conditioning coil. Under winter operating conditions, conditioning medium is supplied through line 01 and passes through the, branch line I52 containing check valve I 52a, to junction I53. Part of the conditioning medium travels through the pipe I41 and enters the valve at connection I04 and passes downwardly therein and is discharged from the valve through connection I05. The other portion or the conditioning fluid passes from the junction I53 to the conditioning coil 99, is dis-. charged therefrom through line I48 and through portion of the valve from I06 to I00. Converse 1y; if the temperature is lower than' desired, more of the heating fluid will be routed through the conditioning coil and a lesser quantity .will be by- When the valve controlling the action of the heat exchange coil 99 is controlled manually,

- there is no necessity for reversing the -tlow ,of

the conditioning medium through the pipes, 03

and 91 as in the case or automatic'control in t e o diillculty in determining whether the unit was readily turn the valve in either direction as required to bring about the desired change inthe conditioning action. Thus, under summer operating conditions, when the local unit is supplied erator will depress the valve I so as to permit increased flow of cooling medium from opening I05 to opening I04 serving the pipe 108, which delivers conditioning medium to the coil 99; and if the temperature is too low the operator will adjust the valve tov raise the valve member I so that a lesser quantity of cooling medium flows through the conditioning coil 99. Under winter operating; conditions, when heating medium is supplied to. the conditioning unit the operation is merely reversed. Thus, when the' temperature in the enclosure is too high, the operator will raise the valve IM to diminish thesupply of heating medium to the coil 99 through the pipe I08,

and if the conditioned-enclosure is too cold, the valve I4I will be depressed to permit a greater supply of conditioning medium to the coil 99 through the connection I08.

During intermediate seasons, however, certain operating difllculties tend to arise. Thus, under certain conditions some of the zones of a conditioned enclosure may require heating while others require cooling. Under such conditions the central station apparatus woul be operative for supplying cooled and dehumi ifled primary air to all zones, but the local zone control device 51 might cut off the supply of cooling medium to a zone requiring heating and instead might turn on the steam to warm the water circulated to and through the local units of such zone. Under such circumstances an operator seeking manually to adjust the valve might have some being supplied with hot or cold water. Thus, if the operator put his hand over the air outlet grille of a unit supplied with hot water, he might experience a sensation or cooling arising from the relatively low dewpoint of the air and its relatively high velocity, although the delivered air might supplied with cool water and, feeling too warm,

he would naturally open the valve wider. It in fact the unit was being supplied with warm water, such increased opening of the valve would naturally aggravate his discomfort. Thus, there is.

indicated a need for a device which will positively indicate to the operator-the direction in which the valve should be adjusted to produce a desired change, so that under both summer and winter operating conditions, and regardless of whether the unit is being supplied with warm water or cold water, the operator will at all times be enabled to make the required adjustment promptly and without experimentation.

- To this end there is preferably provided an arrangement such as illustrated. in Figs. 6-8, which automatically indicates the direction in which the valve should be turned to provide for desired resulation of the room temperature, regardless of whether the unitls being supplied with hot water .or cold water.

As illustrated, a thermal bulb I94 is placed in heat exchanger-elation with the water supplyexpansible bellows I56 carries'a slide plate I51 bearing suitable indicia indicated at I58. The slide plate I51 may be supported .by suitable flanges or the like I 59 and the plate I51 is mounted Just beneath the top I 60 of the conditioner casing, preferably at an end thereof. In the top of the conditioner casing are provided a plurality of apertures, one of these being designated I6I and the other I62. When the unit 53 is being supplied with cold water, the bellows I56 will be relatively contracted and the marking "W" or "Warmer" or the like may then be visible through the aperture I6I while the marking 0" of Colder or the like may be visible through the aperture I82. Thus, under summer operating conditions, or when cold water is being supplied to the unit, the operator will turn the valve handle H2 in a clockwise direction as seen in Fig. 7 to increase the cooling effect. and in a counter-clockwise direction as seen in Fig. 7 to decrease the cooling effect. Under winter operating conditions, or when heating medium is being supplied to the local unit 53, the bellows I56 will be caused to expand. This will move the slide I51 and the indicia visible through the apertures I60 and I62 will therefore be reversed. Therefore, if an operator under winter operating conditions feels too warm the valve handle H2 will then be turned v in a counter-clockwise direction as seen in Fig. 7 to increase the conditioning effect, and if he feels too cool. the valve handle will be turned in a clockwise direction as seen in Fig. '1. As will be understood, the valve handle is so arranged that adjustment of the handle in accordance with the position of slide I51 will effect the required adjustment of valve closure member MI.

It is to be understood that the adjustable indicator mechanism illustrated in Figs. 6-8 is employed only because the direction of flow of the conditioning medium is the same regardless of whether the conditioning medium is hot or cold.

I! desired, the cross-over pipes 12 and 14, and the three-way valves 13 and 15 described in connection with zone .A of the system, may be incorporated in zones such as B in which the local units are manually controlled. and in Sllch case there will be no need forproviding the adjustable indicator mechanism of Figs. 6-8 which changes its position in accordance with the temperature of the conditioning medium. If the changeover arrangement is employed for reversing the flow in the adjustment of the change-over valves in response to changes in the temperature of conditioning medium made available for supplyto the zones served thereby, no detailed showin of such control apparatus for the valves is deemed necessary here.

Referring now to Fig. 9, which illustrates a section of one of the high pressure air risers, and a portion of a lateral connection extending therefrom, the latter being shown in an exploded view, 52 designates the vertical riser which replaces, in the present invention, the relatively large and expensive distribution ducts of conventional air conditioning systems. The riser pipe 52 is of relatively small dimensions and comprises a tube of suitable metal or the like; It may comprise, for example a welded tube of galvanized steel. While it is to be understood that the size of the riser 52 will vary in accordance with the requirements of particular installations,

- and the amount of air a particular section is reaccordance with whether heating or cooling is I being effected by the conditioning medium, an operator will always turn the valve in one direction if the enclosure served b the unit is too warm,

and will always turn the valve in the opposite direction if thaenclosure served by the unit is too cold.

It is to be understood, moreover, that while the valves 13 and 15 have been described as being three-way valves, the reversal of flow may be efl'ected by the use of ordinary shut-oil? valves arranged in a manner well understood in the piping art. These change-over valves may be controlled manually but preferably are arranged automatically to change their position in accordance with the temperature of the condition ing medium made available for delivery to the local units 01' any zone, and as explained above, the temperature of the conditioning medium made available for supply to any particular zone is controlled in accordance with the particular requirements of that zone. Thus. cold water may be circulated through other of the zones. Since any well-known means may be used for effecting .bear against the outer end quired to handle, the diameter of the riser pipe will generally be of the order of about 6". This is in marked contrast to the relatively large ducts required in conventional systems for distributing conditioned air from a central conditioning point to a plurality of remote enclosures served by the system. Thus, these conduits have an area of only about 7 to 10% of the area occupied by conventional ducts. Al'so,,it will be appreciated that installation and assembly of risers comprising sections of pipe, such as 52, may be accomplished quickly and readily at relatively low cost. The vertical risers are assembled from separate sections which are joined together by suitable joints such as illustratedat I6I, the preferred manner of Joining the various sections of the riser 52 being shown more particularly in Fig. 11.

The exploded view portion of Fig. 8 and Fig.

10 illustrate a preferred method of connecting desired construction. Preferably, the flexible conduit is of that type illustrated in Fig. 10 which is well known in the art. I65 designates a gasket 01' any suitable compressible material, preferably neoprene, and I66 designates ametal follower ring, preferably formed of brass or the like, which abuts the gasket and causes the latter to of the pipe nipple I62. A screw cap I61 having an internally threaded cylindrical flange, engages the threads of the pipe I62 so as-to take up on the follower ring and gasket. The other end of the flexible conduit I65 is suitably secured to the laterally extending tube I68 which extends tothe unit or units served by the lateral connection generally designated 54. Preferably, the flexible conduit is secured to the pipe I68 by being soldered thereto at I69 and by means of rivets or the like indicated at 110. 1

It is to be understood that the primary air within the risers 52 must at all'times be at a from; the central station for providing the desired induction effect when the high pressure air is discharged within the local unit. Thus, it

the order of about 1" of Water.

provide the desired induction effect. Delivery of air within the unit at too high a pressure results in excessive velocity, noisy discharge, and an excessive rate of air circulation. Therefore, it is necessary to provide suitable means for reducing the pressure of the primary air which is delivered to the various local units.

In operation, the pressure in the primary air riser may be' of the order of 4"v of water, whereas the optimum pressure within the plenum chamber 85 of each local unit will preferably be of To accomplish the necessary reduction of pressure in a noiseless manner, the pressure is preferably reduced in stages. To this end there is provided an orifice ring "I within the-pipe nipple I82. The orifice ring I". has a relatively small opening I12 formed therein, the size of the opening being determined in accordance'with the amount of pressure reduction which isto be effected by the orifice ring. As will be understood, the smaller the opening the greater will be the pressure reduction. The additional or secondary stage of pressure reduction 'is accomplished by the valve 81 disposed at the air entrance 88 to the plenum chamber of eachlocal unit. Reduction'of the pressure in this manner assures simplicity in construction and quietness and emcacy in oper- '2,aos ,o4s' v 'culation pipes 88 and 81, and a suitable drain pipe I82 communicating with the drain pipes 8 of the local units. All of the vertically extendcomprises a structural section I84 and an outer ation. Where there is a relatively small pres- Referring more particularly to Fig. 11 illustrat- 1 ing the manner in which the various sections of the riser 52 are assembled, the section 82a of the riser pipe 521s belled at its upper extremity as indicated at I13, and the upper section 52b of the riser pipe 52 is disposed within the belled portion I13 of the lower section. The bottom extremity of the section 52b is preferably belled slightly outwardly as indicated at I18, the portion I14 abutting the shoulder I18 formed at the bottom of the belled portion I88. An air-tight and mechanically strong joint is assured by the provision of a wedging member generally designated I18 disposed between the belled portion I18 and the lower portion of the pipe section 82b. The inner surface of the wedging member I18 is cylindrical but the outside thereof is tapered to conform to the taper atth'e inside of the belled portion I13. The 1.1088011111011105 I11 of the wedging member I18 is continuous, as is I also the intermediate section I18 which is formed with a somewhat smaller outer diameter than the lower section I11 to provide a groove I18. The upper portion I88 of the wedging member I18 is provided with a pluralityof vertically extending slits I8I. By forcing the wedging member I18 tightly within the space between the belled portion I18 and the lower portion 'of section 82b, an air-tight and mechanically strong joint may be effected readily and quickly, without resort to solder or any other bonding or sea]- ing material.

Fig. '12 is a horizontal section taken through a portion I of finishing plaster or the like. It will be notedthat the connection pipes 86 and II of the water circulating system connecting with the water circulating riser 63 and 81 are looped around the air riser 52 so that the bends thus formed in these connecting pipes may provide for suitable expansion and contraction due to changes in temperature of the circulated conditioning medium. Preferably, the water circulating pipes are insulated in any suitable manner.

It will be understood that the vertical risers will not always be in immediate proximity to the local units, and it will therefore be required to run short lateral connections from the vertical rr'ser and water pipes to the local units. In order that these laterally extending connections-may be concealed from view, there is provided the baseboard arrangement illustrated in Figs. 13-15. As shown, a plurality of brackets I88 are secured to the wall of a room in any desired manner,

as by screws I81. The upper extremities of the brackets I88 are provided with belled portions I88 behind which there is adapted to be positioned ,the downwardly extending flange I88 of a baseboard cover piece I88. The lower portion of the cover piece is received within a pocekt formed between an upwardly extending leg I8I of the bracket and a belled portion I82 of an upwardly extending member I83 suitably secured in any desired manner to the leg I8I of the bracket.

Within the space thus formed there is also inserted the downwardly extending flange I84 orf-a base protecting plate I85 formed of suitable materlal adapted to withstand the corrosive action of cleaning agents which might come in contact therewith when the floors of the conditioned enclosure are cleaned. Mounted within the channel formed by the cover plate I88 is a drain trough I86 secured,- as by screws I81, to the brackets I88. Over the drain pan I88 is positioned the laterally extending air connection 54 and the water connections 88 and IN. Thus, any moisture which might'possibly be precipitated within the baseboard conduit is adapted to be caught by the. drain pan I88, which may deliver the condensed moisture to drain pipe I I8 as by means of a. suitable connection I88. It will be appreelated-that the cover piece of the baseboard assembly may be removed very readily to provide immediate access to the lateral air and water connections. Also, the baseboard assembly may be installed very quickly and conveniently and with the assurance that the assembly after com-' pleted will provide a finished and attractive appearance and will effectively conceal the lateral pipes connecting the unit with the vertical when it is necessary to extend the lateral connections to a wall or partition, this may be accomplished neatly by means of the finishing piece I88 illustrated in Figs. 14 and 15. The finishing piece may be used in conjunction with vertically extending assembly used for containing a conventional wood molding 288 so that-the finished assembly, will be entirely attractive as well as mechanically satisfactory- If desired, a small quantity'of the-air condi: tloned in the central station conditioning apparatus may be. discharged within the space "I surrounding, the vertically extending and water connection and drain pipes. As will be understood, the air thus conditioned has a relatively low dewpoint and hence effectively prevents condensation upon the outer surfaces of the water supply or other pipes of the riser system; As pointed out above, the dewpoint of the air conditioned at the central station will crating conditions have been established. Con

densation will tend to occur only when the system is placed in operation in a humid atmosphere or when there is an abnormal increase in the moisture content of the atmosphere surrounding the pipes of the riser system or in the conditioned enclosures.

Preferably, the front of the plenum chamber 85 of each local unit is provided with a removable plate 202 so that if, for any. reason, access to the interior of the plenum chamber should become necessary, as for purposes of inspection, cleaning .or repair, such access may -be had conveniently.

Figs.,16 and 17 illustrate a valve construction adapted to be employed when manual control of the heating and cooling at the local units is desired. Such a valve is indicated at I03 in Figs. 2 and 3 and also in Fig. 6, except that the valve in Fig. 6 does not include the indicator mechanism disclosed in Fig. 16. The valve I03 is essentially the same as the valve illustrated in Fig. except for the omission of the expansible bellows and the multiplying mechanism which become unnecessary and may be eliminated in the case of manual operation. Thus, the valve includes a casing I2I, a top cap I22 and an actuating stem I 23a, the valve stem I23a being hollow to provide a longitudinally extending channel 203 therewithin. The bottom of the rod 123a bears against an adjustably positioned plate I3Ia and is adapted to cause displacement of this plate. The plate I3Ia is connected to the partition plate I34 by a sealing bellows I32, as in Fig. 5. A rod I33a extends downwardly from the plate I3Ia and is movable therewith to actuate the valve closure member -I4I. The plate I3Ia is provided with a central opening 203 and the rod I3-3a is provided with a channel 204 extending therewithin and constituting an extension through the plate I3Ia of the channel 203 within the valve stem l23a. The handle II2a is secured to the valve stem I23a in any desired manner as by means of a set screw 205 so that as the handle is rotated, the valve stem is correspondingly rotated and raised or lowered by means of the threads 206 to provide the desired adjustment of position of the valve closure member MI.

Within the channels 203 and 204 there is positioned the stem 20! of a thermal indicator having a rotating disc 208 mounted at the top thereof and within a recess 209 formed in the top of the handle lI2a. The .recess is covered by a closure plate 2I0 which isprovided with an aper ture '2II- through which a portion of the indicator plate 208 may be seen. A screw 2I2, or similar means, is employed to rotate the stem of the thermal indicator as thehandle 2:; is rotated so that the relative positions of the indicator disc 208 and the valve handle lI2a. may remain unaffected except by changes in temperature alfectingthe stem 201. Since thermal indicators of this type are well known in the art and in themselves do not constitute a part of the present invention, no detailed description thereof is deemed required here. One type of thermal indicator of the character indicated is.

manufactured by the weston Electrical Instrument Company of Newark, New Jersey, the instruments manufactured by this company, however, being generally provided with a dial pointer rather than a disc as here disclosed. As will be understood, the thermoresponsive stem 201,

extending within andthrough the body of the valve, will respond to changes in the temperature of the fluid passing through the valve and thus will change the position of the disc 208 in accordance with such changes in temperature. The upper face of disc 200 is provided with two sets of arrow indicators pointing in opposite directions and arranged throughout different arcuate portions of the indicator disc. When the conditioning medium circulated through the valveis cold, one portion of the indicator disc 208 will appear opposite the aperture 2, this portion bearing the arrows 2I3. The word Cooler appears upon the cover disc 21I0 proximate the aperture, and when the arrows 2I3 are visible through the aperture 2, this will indicate that to provide cooler conditions in the enclosure the valve handle should be turned in a clockwise direction. This will depress the valve closure member Ill and permit more conditioning medium to enter the pipe I28 and thus pass to the conditioner coils. If the room is too cool under such operating conditions the valve will be turned in a reverse direction to diminish the amount of cooling medium passing to the conditionlngcoil. When the conditioning medium supplied to the valve is warm another portion of the indicator disc 208' will appear through the aperture 2I I, the arrows. 2 then indicating the direction in which the valve should be turned to provide a desired change in temperature within the enclosure. Thus, when heating medium is supplied to the valve, turning the valve in a counter-clockwise direction will render the enclosure 'cooler by raising the valve closure device I and diminishing the supply of heating medium to the conditioner coils, whereas, turning the valve handle in a reverse or clockwise direction will depress the valve closure member I 4| and cause more heating medium to pass to the conditioner coils. It will be apparent to those skilled in the art, that instead of the word Cooler the word Warmer might be applied on the valve handle, in which case the arrows will each pointin a direction opposite to that shown in the drawings, and that variations may be made in the physical embodiment of the invention without departing from the concept herein disclosed.

It will be observed that the system as above described is adapted readily to be installed in existing structures, particularly in those provided with the piping lines customary in steam heating and hot water installations, and that it i be of the order of 30005000 feet per minute instead of-the conventional ducts which occupy a vastly greater amount of space.

Because the number of local units in operation may vary from time to time, it may be desired to employ a static'pressure regulator for maintaining a substantially constant pressure in the primary air means by throttling the supply of air to the mains from the primary fan, or varying the effectiveness of the fan by varying its speed, or by both methods in combination. Since static pressure regulators operating in this way are well known in the art and do not, per se, form part of the invention, although'desirable for use in connection therewith when the number of units in operation is considerably varied from time to time, no detailed description thereof is deemed required here.

Since many changes may be made in the invention without departing from the scope thereof, it is intended that all matter set forth in the above description, or shown in the accompanying drawings, be regarded as illustrative only and not in a limiting sense;

I claim:

1. In combination, a valve having formed therein a first opening, a second opening, a third opening, means providing communication within said valve between said first opening and said second opening, means providing communication within said valve between said second opening and said third opening, throttling means adapted to control communication between said first opening and said second opening, other throttling means for controlling communication between said second opening and said third opening, said first mentioned and'said other throttling means being arranged so that as communication between said firsttwo openings is increased, communication between the last two openings is decreased and vice-versa, a first conduit connecting with said second opening of said valve, 3, heat exchange device, a second conduit providing communication between said first opening and the inlet to said heat exchange device, a third conduit providing communication between the outlet of-said heat exchange device and said third opening,-a cross-connection between said last mentioned conduit and said second conduit, a fifth conduit communicating with said cross-connection, and check valves in said cross section between the fifth conduit and the second and third conduits respectively whereby under summer operating conditions when cooling medium is supplied through said first conduit, increasing restriction of communication between said second and third openings will provide for increased flow of cooling medium through said heat exchange device and viceversa, and whereby under winter operating conditions when heating medium is supplied through said fifth conduit, decreased communication between said second and third openings will result in a decreased rate of circulation of heating medium through said heat exchange device, said fifth conduit serving as a return connection under summer operating conditions when cooling medium 'is supplied through said first-mentioned conduit, and said first-mentioned conduit serving as a conditioning medium return under winter operation conditions when conditioning medium is supplied through said fifth conduit.

2. An apparatus of the character described including' a plurality of air circulating and condi tioning units, a common supply line adapted to deliver conditioning medium to said units, a common return line adapted to receive conditioning medium from said units after circulation therethrough, a source of conditioning medium, means for drawing conditioning medium from said source and from said common return line in varying proportions and for supplying the conditioning medium thus withdrawn to said common supply line at a substantially constant volu-- metric rate, means for withdrawing from said common return line the portion of conditioning medium which is not recirculated to said common supply line, whereby conditioning medium is circulated through said common supply line and through said common return line at a substantially constant and equal volumetric rate, and

flow control means in combination with each of said units for modulating the flow of conditioning medium'through the heat exchange device thereof to provide for modulation of the conditioning effect provided by each of said units.

,3. An apparatus of the character described including a plurality of air circulating and conditioning units, a common supply line adapted to deliver conditioning medium to said units. a common return line adapted to receive conditioning medium from said units after circulation therethrough, a source of conditioning medium, means for drawing conditioning medium from said source and from said common return line in varying proportions and for supplying the conditioning medium thus withdrawn to said com-' mon supply line at a substantially constant volumetric rate, means for withdrawing from said common return line the portion of conditioning medium which is not recirculated to said common supply line, whereby conditioning medium is circulated through said common supply line and through said common return line at a substantially constant and equal volumetric rate, a branch supply line and a branch return line for each unit, and a valve means in combination with each of said units for modulating the flow of conditioning medium through the heat exchange device thereof to provide for modulation of the conditioning effect provided by said unit, and means associated with each unit for bypassing from the branch supply line of the unit to the branch return line thereof, a portion of the conditioning medium delivered to said branch supply line but prevented by said valve means from passing through said heat exchange device.

4. In combination, a plurality of air conditioning units, a fluid circuit for supplying conditioning medium to and returning conditioning medium from said units, said fluid circuit comprise ing a first common conduit serving said units, a second common conduit serving said units, .and an impeller device, means for delivering conditioning medium discharged by said impeller to said units through said first common conduit under predetermined operating conditions, and for returning conditioning medium from said units through said second common conduit under said predetermined operating conditions, and

5. In combination, a plurality of air conditioning units, a fluid circuit for supplying conditioning medium to and returning conditioningmedium from said units, said fluid circuit comprisaseaoes ing a first common conduit serving said units, a second common conduit serving said units, and

an impeller device, means for delivering conditioning medium discharged by said impeller to said units through said first common conduit under predetermined operating conditions, and for returnin conditioning medium from said units through said second common conduit under said predetermined operating conditions, and means for delivering conditioning medium discharged from said impeller to said units through said second common conduit under other predetermined operating conditions, and for returning conditioning medium from said units through said first common conduit under said other predetermined operating conditions, whereby under said diiierentv operating conditions conditioning medium is circulated in diflerent directions auxiliary conduit means providing communication between each of said units and said first and second common conduits, a heat exchange device in each of said units, said auxiliary conduit means being arranged to supply to said heat exchange device conditioning medium received from one of said common conduits and also to bypass a portion of said conditioning medium around said heat exchange device, said conduit means being arranged to return both portions of said conditioning medium to the other common conduit, and proportioning valve means in combination with said auxiliary conduit means for variably proportioning the .flow of conditioning through said flrst'and second common conduits,

medium at each unit through the heat exchange device thereof and bypassing the heat exchange device thereof, a thermo-responsive control element operatively connected with said proportioning valve means and adapted variably to control the flow of conditioning medium through and around the heat exchange device of said unit. said proportioning valve means being arranged whereby when conditioning medium is supplied through one 01' said common conduits, increased temperatures aflecting said thermo-responsive device will cause said device to efiect increased flow of conditioning medium through said heat exchange device and, vice-versa, decreased flow 6. An apparatus of the character described including, in combination, a plurality of air conditioning units each containing a heat exchange device, means forming a'first fluid circuit including means for cooling conditioning medium circulated through said circuit, means for cir-' culating air in heat exchange relation with said medium and delivering said air to the units means forming a, second fluid circuit including said units, means for drawing conditioning medium from said first mentioned circuit and for circulating said withdrawn conditioning medium through said second circuit and the heat exchange devices of the units thereof in response to demand for cooling. by said units, said last mentioned means including valve means and a thermo-responsive control device in control thereof, said valve means and the control device J to return conditioning medium therefrom, and

including means for reversing the direction of fluid flow through said first and second headers.

8. In an apparatus of the character described, including a central conditioner and a plurality of local units each havinga heat exchange device therein, a riser casing, a primary air conduit within said casing for supplying air from said conditioner to said units, a first conduitwithin said casing and a second conduit within 'said casing for respectively supplying conditioning medium to and returning conditioning medium from said units, means for circulating said 45 mediumthrough said central conditioner, means responsive to decreased temperature, and whereby under said other predetermined operating conditions when conditioning medium is supplied through the other of said common conduits, increased temperatures affecting said thermo-responsive control device will have the cf fect of causing said device to decrease the rate 01' down! conditioning medium through said heat exchange device and decreased temperatures affecting said theme-responsive control device will have the eflect of increasing the rate oi'flow through.

of conditionin medium there for conditioning primary air in said conditioner by circulating it in heat exchange relation with said medium, means for circulating said medium through said conduits subsequent to its employment for conditioning said primary air, and,

means for admitting within said casing a quantity of said primary conditionedv air, said air having a dew point lower than the temperature of the conditioning medium in said conduits whereby the formation of condensation on the outer surfaces of said conduits is prevented. 

